package com.ztom.v2;

/**
 * @author ZhangTao
 */
public class Code27MergeTwoSortedLists {

    public class ListNode {
        int val;
        ListNode next;

        ListNode() {
        }

        ListNode(int val) {
            this.val = val;
        }

        ListNode(int val, ListNode next) {
            this.val = val;
            this.next = next;
        }
    }

    public ListNode mergeTwoLists(ListNode list1, ListNode list2) {
        if (list1 == null) {
            return list2;
        }
        if (list2 == null) {
            return list1;
        }
        ListNode dummy = new ListNode(-1);
        ListNode cur = dummy;
        ListNode l = list1;
        ListNode r = list2;
        while (l != null && r != null) {
            if (l.val < r.val) {
                cur.next = l;
                l = l.next;
            } else {
                cur.next = r;
                r = r.next;
            }
            cur = cur.next;
        }
        while (l != null) {
            cur.next = l;
            l = l.next;
            cur = cur.next;
        }
        while (r != null) {
            cur.next = r;
            r = r.next;
            cur = cur.next;
        }
        return dummy.next;
    }

    public ListNode mergeTwoLists1(ListNode list1, ListNode list2) {
        if (list1 == null) {
            return list2;
        }
        if (list2 == null) {
            return list1;
        }

        if (list1.val < list2.val) {
            list1.next = mergeTwoLists1(list1.next, list2);
            return list1;
        } else {
            list2.next = mergeTwoLists1(list1, list2.next);
            return list2;
        }
    }
}
